|Publication number||US7023343 B2|
|Application number||US 10/472,088|
|Publication date||Apr 4, 2006|
|Filing date||Mar 19, 2001|
|Priority date||Mar 19, 2001|
|Also published as||CN1240028C, CN1511307A, DE60110939D1, DE60110939T2, EP1371040A1, EP1371040B1, US20040080417, WO2002075686A1|
|Publication number||10472088, 472088, PCT/2001/412, PCT/IB/1/000412, PCT/IB/1/00412, PCT/IB/2001/000412, PCT/IB/2001/00412, PCT/IB1/000412, PCT/IB1/00412, PCT/IB1000412, PCT/IB100412, PCT/IB2001/000412, PCT/IB2001/00412, PCT/IB2001000412, PCT/IB200100412, US 7023343 B2, US 7023343B2, US-B2-7023343, US7023343 B2, US7023343B2|
|Inventors||Poul Richter Jørgensen|
|Original Assignee||Kobe Properties, Ltd.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (8), Classifications (11), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates to a method of producing a deactivatable RF resonance circuit (tag) for use in an electronic article surveillance system (EAS system).
Such resonant tags for use in EAS systems, also called resonant labels, are well known in the art. Usually such tags comprise a supporting layer formed of a dielectric material with conductive layers on its front and rear faces. One of the conductive layers on one face of the dielectric support is shaped to form an inductive component and the first part of the capacitive component whilst the other conductive layer on the other face of the dielectric support is shaped to form the second part of the capacitive component of the resonant tag.
The resonant circuit of the tag is supposed to have a high quality factor (Q-factor or Q-value).
In use a transmitter in the EAS system is emitting signals having frequencies, which are systematically varied within a specific range. When the resonant frequency of the resonant circuit of the tag is within this range, a receiver will be able to detect the presence of the tag (of the resonant circuit) when the natural frequency of the resonant circuit is emitted.
When articles provided with resonant tags are passing by the cashes at the exit of the premises where the accounts are to be settled, the removal or destruction of the tags has to take place. If this would not be done the receiver of the EAS system is detecting the attempt to pass the control area and is activating an alarm.
In order to modify the resonant circuit for its deactivation it is known to provide regions with a reduced distance between the capacitive components (capacitor plates), so that the field strength applied for deactivation will provoke a breakdown at such regions.
One solution has been proposed in U.S. Pat. Nos. 4,498,076 and 4,567,473 disclosing a method of producing a resonant tag with a circuit suitable for modification. It is proposed to create a reduced (small) distance between opposite capacitor plates of the resonant circuit, i.e. at predetermined points, by locally pressing one conductive layer down into the dielectric material of the support (impressing a notch). The remaining thickness of the dielectric material at these places becomes smaller than outside of these regions. As according to general knowledge of physics a breakdown will always occur at the place with the smallest distance, the breakdown in the capacitor will always occur through the remaining thickness of the dielectric material at this region of reduced thickness and allows furthermore to use a lower breakdown voltage than outside such a region.
This solution presents however a number of disadvantages or at least difficulties, as local compression of the dielectric material to a required minimal remaining thickness of the material (necessary to avoid the risk of an unintentional short), e.g. in the order of μm in a limited region, requires a very precise angle of 90° between a pin performing the compression and the plane of the capacitor plate and a precisely controlled pressure to obtain usable reproducible results.
The major disadvantage of the aforesaid solution is that breakdown has always to happen through the remaining thickness of dielectric material between the capacitor plates in said compressed area. When the electric arc that causes breakdown passes through the dielectric material it risks often to burn off and forms a short circuit of charred plastic material with the result that the short circuit between the two capacitor plates consist of a mix of charred plastic and metal, resulting in a mechanically very unstable short circuit. This known solution leads to a product that easily becomes reactivated, which of course is not acceptable.
Another disadvantage, resulting from the fact that the electric arc must pass through the dielectric material left after compression is that a higher breakdown voltage is needed than if breakdown could occur through a material-free space (e.g. air).
In an attempt to avoid the aforesaid disadvantage U.S. Pat. No. 4,876,555 proposes a similar method for producing a deactivatable resonant tag comprising the idea to produce a throughhole through the dielectric material between the opposite conductive layers (e.g. the capacitor plates), thus avoiding remaining dielectric material which requires higher breakdown voltages.
This proposal providing a material free throughhole passing through the dielectric material (support) leaves the conductive layers at their normal level (in order to avoid unintentional shorts). This solution also has a number of disadvantes: The throughholes in the dielectric material, containing only air, are difficult to produce, with the result that in practice no deactivatable resonant tags have been produced in accordance with this method. As an electric arc has to overcome a distance corresponding at least to the thickness of the dielectric material layer a relatively high voltage is needed for producing the breakdown for deactivating the circuit (a distance corresponding to that between the capacitor plates). This results in that there is no practical advantage compared with the state of the art described.
Finally EP patents No. 0 509 289 and No. 0 750 285 are disclosing methods of producing shorts between the conductive layers (e.g. between the opposite capacitor plates) by using heated pins and an electric current for locally melting away the dielectric material between said conductive layers and electrically welding together such layers, followed by electrically interrupting such a connection to form two opposite electrodes at varying distance between which a further conductive bridge (in form of a filament) is formed (using appropriate voltage), followed by a further interruption of the thus connected electrodes to establish a new gap of predetermined width between the electrodes ready for deactivation.
Although this process is satisfactory, it is rather complicated and leads to electrode gaps, which may at least slightly differ from product to product (difficult to check the quality).
It is therefore an object of the present invention to find a novel and simple method of producing deactivatable tags of highest quality having a resonance circuit with a high Q-factor and having as small as possible a material free distance (deactivation area) between two opposite capacitor plates. The method has to be reproducible and must result in even products of highest quality with a minimum of material to be rejected.
The aforementioned object of the invention is achieved in a surprisingly simple manner by performing the inventive steps recited in claim 1.
Preferred embodiments of the invention are defined in the depending claims.
The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. The description makes reference to the annexed drawings, wherein:
As shown by the drawings the opposite conductive layers with a supporting layer of dielectric material are first short circuited by using a heated tool of small diameter, thereby displacing the dielectric material in the zone of the short-circuit and permanently deforming one of said conductive layers. Such deformation is possible due to the plasticity of the metal (e.g. aluminium) forming the conductive layers. When forming the short, the other conductive layer is also slightly deformed (depressed) as shown by
Therefore, the short circuit is precisely controlled by means of the shape of the tool, the temperature, the period of time the tool is in contact with the capacitor plate, and the weight of the tool or the pressure from the tool; all parameters are controlled electronically and mechanically.
A weight of 200 g and a tool temperature of 400° C. combined with a period of time of 1.2 sec. has proved in tests to give a stable and even short circuit.
After the short circuit has been established between the two metal surfaces (capacitor plates), the short circuit is checked by means of electronic measuring. This measuring checks whether a satisfactory short circuit has been obtained. In case the short circuit is not satisfactory, the product will be rejected as being defect When the measuring shows the short circuit is found good, the two metal layers will be crimped in a special crimp area to form a complete resonant circuit, thus giving the tag the required frequency (the crimp will connect one of the conductive layers with the opposite conductive layer in a known manner).
Thereafter the short circuit is removed electrically or mechanically as e.g. schematically shown in
The developed process described herein above ensures that:
After the check and the crimp between the two conductive layers, the short circuit as shown in
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US5187466||Jul 22, 1991||Feb 16, 1993||Kobe Properties Limited||Method of deactivating a resonance label|
|US5510770 *||Mar 30, 1994||Apr 23, 1996||Checkpoint Systems, Inc.||Surface deactivateable tag|
|US5608379 *||May 20, 1994||Mar 4, 1997||Sensormatic Electronics Corporation||Deactivatable EAS tag|
|US5608380 *||May 18, 1995||Mar 4, 1997||N.V. Nederlandsche Apparatenfabriek Nedap||Deactivation and coding system for a contactless antitheft or identification label|
|US5841350 *||Jun 27, 1997||Nov 24, 1998||Checkpoint Systems, Inc.||Electronic security tag useful in electronic article indentification and surveillance system|
|US6400271 *||Mar 20, 2000||Jun 4, 2002||Checkpoint Systems, Inc.||Activate/deactiveable security tag with enhanced electronic protection for use with an electronic security system|
|EP0750285A2||Oct 9, 1995||Dec 27, 1996||Kobe Properties Limited||Method for manufacturing a deactivatable resonance label|
|WO1992009978A1||Nov 20, 1991||Jun 11, 1992||Joergensen Poul Richter||Method of producing tags comprising resonant circuits which can be activated and deactivated|
|U.S. Classification||340/572.3, 340/572.1|
|International Classification||G08B13/24, G08B13/14|
|Cooperative Classification||G08B13/242, Y10T29/49002, G08B13/244, G08B13/2437|
|European Classification||G08B13/24B1G2, G08B13/24B3M, G08B13/24B3M1|
|Oct 11, 2005||AS||Assignment|
Owner name: KOBE PROPERTIES LTD., GREAT BRITAIN
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Effective date: 20031024
|Sep 2, 2009||FPAY||Fee payment|
Year of fee payment: 4
|Sep 11, 2013||FPAY||Fee payment|
Year of fee payment: 8
|Dec 9, 2015||AS||Assignment|
Owner name: ALL-TAG SECURITY S.A., BELGIUM
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:KOBE PROPERTIES, LTD.;REEL/FRAME:037251/0860
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